"The brutal killings in the Central African Republic are creating a cycle of murder and reprisal that threatens to spin out of control," Peter Bouckaert, emergencies director at Human Rights Watch, said in a statement Thursday.
Bouckaert published a 34-page report based on field work conducted in northern CAR. It found the anti-balaka, a Christian militia, have killed "several hundred" Muslims since September.
The Seleka rebel coalition, a predominately Muslim group, toppled the CAR government in March. Reprisals from their Christian rivals prompted the U.N. Security Council to authorize a French military intervention to support an African Union peacekeeping effort in the country.
Human Rights Watch said the Christian militia describes itself as a self-defense force but its actions suggest it's waging a deliberate campaign against Muslim communities.
Bouckaert said he was frustrated the U.N. Security Council hasn't done more to address the crisis.
"Urgent support for peacekeeping in the Central African Republic is crucial to bring stability to a tense situation, protect the population from abuses, and ensure that humanitarian aid reaches those at grave risk," he said in a statement from Nairobi. "The potential for further mass violence is shockingly high."